The instant invention relates to a process and device to spool a yarn on a conical bobbin or former subsequent to bobbin replacement or yarn breakage in an open-end spinning machine. DE OS 28 50 729 and DE 28 50 729 C2 disclose a method by which a yarn storage is incorporated into the course of the yarn by which the yarn reserve between the piecing device and the conical bobbin take-up is kept at least partially filled before the clamping roller is pressed against the draw-off roller, i.e. before the yarn is drawn off by the machine's pair of draw-off rollers during piecing in an open-end spinning device and subsequent winding of the spun yarn on a conical bobbin and to empty the yarn storage before yarn transfer to the spooling frame of the spinning machine. It is the purpose of DE 28 50 729 C2 to avoid thick spots and weak spots in the yarn during piecing as well as errors after the winding process with the utilization of conical bobbins.
DE OS 17 85 153 discloses a device used to spool conical cross-wound bobbins in which a yarn storage is provided to compensate for the irregularities in the course of the yarn which are caused by the utilization of conical bobbins. DE OS 25 41 589 discloses a device for automatic piecing in an open-end spinning machine.
In all known processes according to the present state of the art the yarn supplied by the spinning device is first handled by a service unit, whereby the yarn is withdrawn from the spinning device by a draw-off device of the service unit and is conveyed to the bobbin of the spinning machine by various levers and graspers of the bobbin. The bobbin can also be driven by a drive of the service unit. While the yarn is handled by the service unit, and also at the moment when the yarn is already being conveyed from the spinning device to the bobbin, no back-and-forth winding of the yarn on the bobbin takes place. Only when the yarn has been securely applied to the cross-would bobbin is it transferred to the yarn guide of the spooling station for cross-wound spooling on the bobbin of the service unit, making it possible for the normal spooling of a cross-wound bobbin to begin or to be continued. At the yarn is transferred from the service unit to the cross-winding device, a transfer to the draw-off device of the spinning machine is generally carried out at the same time. The process for piecing and subsequent transfer of the yarn to the spooling station of the spinning machine are well known according to the present state of the art.
In addition to cylindrical bobbins, an ever increasing number of cross-wound bobbins is being spooled by the spooling devices of open-end spinning machines. The transfer of the yarn by the service unit to the spooling device, by hand when manual piecing is carried out, produces brief tension peaks in the yarn at the moment when the cross-winding device grasps the yarn. This is especially troublesome when conical bobbins are spooled. Excessive yarn tension then occurs and risks causing yarn breakage. If the yarn is conveyed in the direction of the larger diameter of the conical bobbin when it has been grasped by the yarn guide, the effects of different circumferential speeds in conical cross-wound bobbins is added to the stress on the yarn produced as it is being grasped by the yarn guide. If the yarn is immediately conveyed in the direction of the larger diameter of the former or bobbin when it has been grasped by yarn guide, yarn breakage occurs more frequently.